Uncertain how quickly he could recover, the Yankee decided to place Andy Pettitte on the DL.(AP)

One day after leaving his start in the fifth inning, Andy Pettitte has been placed on the 15-day disabled list with a strained trapezius muscle, and the Yankees will recall lefty Vidal Nuno from Triple-A Scranton/Wilkes-Barre to take his place.

"We don't think it's overly serious but we want to play it safe," Yankees general manager Brian Cashman said Friday afternoon. "Thankfully it's Minor, but this is the course of action we're going to take, and everyone is in agreement. I know Andy understands it; he's been around long enough to know this is in our best interest. Of course we'll miss him, but we'll get him back."

Pettitte left Thursday's game after 4 2/3 innings after his trapezius muscle locked up; he said after that game that he had a heat massage between the fourth and fifth innings but the muscle locked up again right afterwards, and Cashman described the decision to DL him as precaution to prevent that again.

"He was pretty spasmed up yesterday, and it's been something he's been feeling," Cashman said. "He wouldn't start for five days for us, and timing was an issue, especially given his age and the time of year. I'm not in the position to be able to carry an extra player until the situation is resolved, and that's probably not in his best interests, so I'd rather take care of this now and resolve it."

Pettitte said it's always disappointing to go on the disabled list, saying he always wants to pitch every fifth day, but he understood the thought behind giving him 15 days.

"I think it could be overly cautious, but I also understand that I probably need a few days to let it calm down before I throw a bullpen," Pettitte said. "I'd need to pitch on Tuesday, and they don't want to send me out there and get warming up and have it lock up and then we're out a pitcher. We're in a tough stretch right now, and I understand it's early."

With that, neither Pettitte nor Cashman thought this was something that would keep the lefty out longer, and he himself said it might be a blessing in disguise to give him time to re-evaluate his training regimen.

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"I'm in the mindset of 'okay you're DL'ing me, so maybe let's take a little blow,' and I'll probably take 5 or 6 days and do nothing to give my body a rest," Pettitte said. "I think everybody has been trying to figure out if (the heavy between-start workload) is an issue, but maybe that's something I need to look at, and maybe I need to look at all the running I do. I'm going to try to look at everything."

In addition, neither man thinks the current injury is related to the back spasms that cost the southpaw a start earlier in the season, with Cashman saying that "I don't think it's the case, but we're here regardless."

As for Pettitte's replacement, Nuno, who pitched five scoreless innings in Cleveland on Monday, was due to start for Scranton on Saturday, but Cashman said he's not sure whether he will be slotted into Pettitte's spot and pitch Tuesday or if Larry Rothschild will deploy him sooner and push some of the rotation back a day.

One thing he did say, however, is that Ivan Nova was not a consideration.

"No, we have to just run him through the circuit first to make sure everything he had was resolved," Cashman said. "His arm was good, but it's what he had with his rib cage that made him not a consideration."